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The high-strain direct testing method is a novel technique for dynamic testing of pile bearing capacity, developed as an improvement to the traditional high-strain method. While its theoretical feasibility has been demonstrated through numerical simulations and laboratory experiments, its effectiveness in practical engineering applications remains uncertain. This paper discusses the foundational theory of the high-strain direct testing method, highlighting its clear calculation principles, straightforward process, and advantage of not requiring iterative fitting. The bridge project in Zhuhai, Guangdong Province, China, serves as a case study. An instrumentation layout for concrete-filled piles was designed based on the principles of the high-strain direct testing method, and data processing and analysis programs were developed using Python. Fifteen test piles were selected for field application of the high-strain direct testing method, with detailed analysis conducted on the results from four test piles. The test results were consistent with the soil layer distribution characteristics beneath the four piers of the bridge, validating the feasibility of this method in actual engineering practice. Subsequent static load tests on these four test piles allowed for a comparison with the high-strain direct testing method results, confirming the accuracy and reliability of the high-strain direct testing method for determining the bearing capacity of single piles. Furthermore, this paper identifies sources of error in the application of this method and proposes corresponding improvement measures. As this method directly derives results from instrumented measurements, it is theoretically applicable to piles of any cross-sectional shape and material, provided that enough measurement lines can be successfully arranged along the pile shaft. This capability allows for the real-time estimation of the ultimate bearing capacity during pile driving, thereby enhancing the universality of the high-strain direct dynamic testing method beyond traditional techniques. [ABSTRACT FROM AUTHOR]

The main objective of this paper is investigation of clayey soil setup effects on axial "resistance" and "stiffness" of small-scale piles with special attention on "overconsolidation ratio" (OCR) and "installation method". A consolidation chamber is developed and an instrumented model pile is either driven or jacked-in through saturated consolidated Kaolinite clay at different OCRs of 1.2 (normally consolidated, NC) and 4.8 (over consolidated, OC). The pile was static load tested at different time intervals of 1 h through 90 days. Higher pore pressures are induced during pile installation in NC compared to OC clay. The frictional resistance of OC soil is higher than NC at end of drive as well as end of setup in both driven and jacked-in piles. The frictional resistance of jacked-in piles is greater than driven piles at end of drive, but due to higher rate of setup, the long-term frictional resistance of driven piles is shown to be greater, attributed to more disturbance of the soil during installation of driven piles. Attempts are made to differentiate between the contributions of dissipation of excess pore pressure and non-pore pressure components for each consolidation condition and pile installation method. A relation is proposed to quantify the pile stiffness variations over time due to soil setup. [ABSTRACT FROM AUTHOR]

It is important to appraise the performance of the steel pipe pile performance in harbor engineering. The load transfer mechanism and pile-soil interaction could not be clearly understood using the traditional measurement. In this case, fiber Bragg grating (FBG) and Brillouin optical time domain reflectometry (BOTDR) were applied simultaneously at an open-ended steel pipe pile field test in Ganyu Port, China. Results showed that the fiber optic sensing system accurately measured the axial force, side friction, and bearing behaviors of open-ended steel pipe piles based on strain data. During the pile driving stage, the system captured the bending deformation and eccentric load on the upper part of the pile above the mud surface, identifying the relatively large tensile strain at the final stage of driving. For the static load test, the strain and resistance distribution obtained by sensing systems suggested that 80% of pile compression was concentrated in the upper 20 m, and the maximum force was observed at the location of soil surface. The precision of high strain dynamic tests is limited for complex field conditions and model's parameters-setting. [ABSTRACT FROM AUTHOR]

The field static load test method was adopted for two test piles in a project in Zhejiang area of China, analyze the effect of post-grouting technique on super-long cast-in-place bored pile and its internal mechanism. Q-s curves and pile axial force curves were drawn based on test data to show that post-grouting technique played a prominent role in improving bearing capacity of single pile and pile skin friction. In addition, pile skin friction at upper soil layer around super-long pile was fully used, but that at lower soil layer was not. For the design of super-long pile, the compression of pile body should be considered to make the best use of pile skin friction caused by relative displacement between pile and soil. [ABSTRACT FROM AUTHOR]

This paper presents a new approach of estimating pile setup starts from the end-of-drive (EOD) resistance by the use of a power function model followed by a log-linear function. Often pile setup is estimated using the Skov and Denver(in: Proceedings of the 3rd international conference on the application of stress-wave theory to piles, Canada, 1988) model, which requires knowing the pile resistance at a reference time (to). This requires additional effort for testing the pile at the reference time (to). This effort may cause delay in the foundation construction and thus increasing the cost of construction. Pile load testing program was conducted on seven 914 (36 in.) square close-ended prestressed concrete (PSC) test piles at the Caminada Bay bridge project in coastal Louisiana to develop a methodology to estimate pile setup effectively starting from EOD resistance. Several dynamic load tests (DLTs) were performed on each test pile, with waiting periods of 60 min to 55 days after installation, to measure the magnitude and rate of setup. Static load tests (SLTs) were also performed at the end of the load testing program to validate the results of dynamic load tests. The load testing results showed that the total resistance increased up to 12 times of the EOD resistances after 28 days from EOD. The Skov and Denver (1988) setup parameter “A” was calculated for each test pile using different initial reference times (to). The results showed that the setup parameter “A” was highly variable and uncertain for to less than 1 day. This paper proposes a new power pile setup model that can be used to estimate pile setup immediately after EOD to the initial reference time, to, which is usually 1 day for a log-linear model. The proposed model was validated using results from published case studies for various geological conditions, which shows that the results of the model effectively match the setup test results within a small tolerance. [ABSTRACT FROM AUTHOR]

Static load tests on fully instrumented piles are a useful tool for optimizing the design of pile foundations. By measuring the change in strain along a test pile it is possible to estimate pile-soil interface properties and infer site-specific and technology-specific load-transfer curves to be adopted for design. This paper presents strain measurements obtained from a distributed sensor installed in a continuous flight auger (CFA) pile undergoing a static load test. Distributed sensing was performed using optical frequency domain reflectometry (OFDR), which provided a spatial resolution of 10 mm. The high spatial resolution allowed to highlight local defects, as those produced by undesired variations in the pile cross-section area that can lead to erroneous data analysis if not fully understood. The paper also presents an approach for the derivation of load-transfer curves from continuous strain data. [ABSTRACT FROM AUTHOR]

Static load test program was performed on a single pile and two 16-pile groups with equal and different pile lengths. The soil profile consists of sand fill to 0.5 m depth placed on a thick deposit of soft, normally consolidated and compressible clay. The closed end steel pipe piles in 60 mm diameter were installed from 1.5 m through 2.1 m depth within soft clay deposit. The center-to-center distance of piles in group is about 3 times of pile diameter. The strain gages were installed at one level above and two through four levels below ground surface. Tests were carried out about 7 days after driving by method of a series of load increments placed every 5-min until plunging failure occurred. The load at plunging failure for the single pile, the equal-length pile group and the different-length pile group were about 3, 40 and 48 kN, respectively. The movements at start of failure were about 12, 18, and 17 mm, respectively. The analysis of strain gage measurements indicates that the load distribution on piles in the different-length pile group has become significantly uniform. [ABSTRACT FROM AUTHOR]

Abstract This article shows the mathematical method to determine the lateral stress on the shaft and toe resistance of pile using the new approach. The method was originally invented by Meyer and Kowalow for the static load test. The approximation curve was used for the estimation of both settlement curve and toe resistance curve of the pile. The load applied at the head of the pile is balanced by the sum of two components: the resistance under the toe of the pile and the skin friction. Therefore, the settlement curve is compilation of two factors: the skin friction curve and the resistance under toe curve. The analysis was based on the verification of the methods using laboratory experiments, that is, static load tests. The results of the research allowed to determine the relationship between parameters of the Meyer–Kowalow curve. On the basis of the relationships, it was possible to determine the skin friction and the toe resistance of the pile. Mathematical analysis of curve parameters allowed to determine the influence of the toe resistance on the settlement. [ABSTRACT FROM AUTHOR]

The uplift load test is the most widely used technique for assessment of the performance of micropiles. Although this static load test is easy to perform and interpret, it is expensive, slow to implement, and cannot be used systematically because it destroys the micropile. A new methodology based on a simple low-strain dynamic load test (LSDT) is proposed to develop a systematic and inexpensive method for assessment of performance of a large number of micropiles. The advantage of this methodology is that it is easy to carry out, requires lowimpact energy compared with a classical dynamic load test, and allows immediate interpretation. After describing the proposed methodology, the calibration, and the subsequent validation of the test method, results from full-scale micropiles at an experimental site and three real sites are presented. The results show that the methodology proposed allows confirming micropile performance under service loads in real time without disturbing the micropile. [ABSTRACT FROM AUTHOR]

A research on super-long piles has been primarily based on cast-in-place bored piles. In this article, field tests associated with selected measuring technologies were conducted on two super-long steel pipe piles in offshore areas to investigate the behaviors and performance of super-long steel pipe piles. The strain along the pile shaft was monitored by adopting the Brillouin optical time domain reflection and fiber Bragg grating techniques. Static load tests were also conducted on two test piles to determine the bearing capacities. In addition, the axial forces, relative displacements between piles and soils and pile shaft resistances were calculated based on the measured strain. According to the results of the static load tests, the ultimate bearing capacities of the two test piles are greater than 15,000 and 15,500 kN. Both of these values meet the design requirements. In addition, the two test piles can be treated as pure friction piles, and the load transfer mechanism and relationships between the pile shafts and relative displacements are also discussed. Finally, recommendations for practical engineering and significant conclusions are presented. [ABSTRACT FROM AUTHOR]

In this paper, the CPT-based predicted ultimate pile resistances (R) were compared with the measured pile resistances (R) at different elapsed time for the piles driven into saturated soft clays where piles displayed significant set-up effect. The measured pile resistances were based on 115 restrike records collected from 95 production piles, and 74 records of 9 tested piles. The predicted ultimate pile resistances were calculated from the LCPC, the Schmertmann, and the de Ruiter-Beringen methods, respectively. With the significant pile set-up effect taken into account, the relationship between measured resistances and predicted capacities at different times after pile installation were investigated. The ratios of the measured pile resistances to the predicted capacities scattered in a large spectrum. The ratios fluctuated and stayed within a range of 0.6-1.6 for different CPT methods since end of initial driving until more than 2 months after pile installation. Plots of the ratios versus the predicted pile capacities using different CPT methods have revealed that the ratio (R/R) presented a strong dependence on the predicted capacities. Great research efforts have been devoted to the analyses of the ratios of the 24-h measured resistance to the predicted capacity based on different CPT methods, in an attempt to find a feasible empirical correlation. It is found that a simple linear relationship exists between the quad root of the ratio and the predicted capacity. The developed empirical equations will give pile foundation engineers an insight into the ultimate resistances of driven piles demonstrating significant pile set-up effects. Pile set-up makes pile resistances grow with time, and it might be one of the reasons that cause the frequently reported large discrepancy between calculated static capacity and measured resistance at a certain time after pile installation. [ABSTRACT FROM AUTHOR]

Static Load Test (SLT) is the realiable method to determine bearing capacity of pile foundations. However, SLT is relatively expensive and time consuming compared to Pile Driving Analyzer (PDA) test. Therefore PDA test becoming more populer as an alternative to predict bearing capacity of piles. This paper presents the comparation of ultimate bearing capacity of pile foundations interpreted from Static Load Test (SLT) results and that predicted from PDA tests. Davisson and Chin methods were used to determine bearing capacity of pile foundations interpreted from SLT results. Correlation between bearing capacity of piles embedded in sand and clay layer interpreted from SLT and PDA test was analyzed. The result shows that bearing capacity of piles which determined based on Static Load Test interpreted using Davisson and Chin methods exhibit relatively better agreement with the predetermined ultimate bearing capacity. Almost all records of bearing capacity of pile foundation embedded in sands layer interpreted from SLT are larger than those predicted using PDA test. While bearing capacity of piles embedded in clays predicted using PDA test varies in relatively large margin compared to that determined from SLT. [ABSTRACT FROM AUTHOR]

Bearing capacity calculation method and field static load test (SLT) program were carried out simultaneously to study the bearing characteristics of individual Plastic Tube Cast-in-Place Concrete Pile (TC pile), which are increasingly being employed for support of embankments in southeast China. The bearing capacity calculation method considering pile setup (i.e., setup calculation method) was built up according to the cylindrical cavity contraction and horizontal consolidation theories. A series of SLTs on different dates were applied to study the bearing behavior of TC pile and to verify the validity of the established setup calculation method. During TC piles installation, there is about 45% contraction in cylindrical volume due to the extraction of steel casing. Both theoretical and experimental results show that the calculated outcomes considering cylindrical cavity contraction agree well with measured ones. The difference value between them is not more than 12%. On the other hand, if the cylindrical cavity contraction is ignored, the calculated bearing capacities of TC piles are overestimated by 160–300%. The setup of TC pile is mainly due to the increment of pile shaft resistance with time elapsed. Cylindrical cavity contraction accompanied by TC pile installation causes much loss of pile shaft resistance. [ABSTRACT FROM AUTHOR]

This paper establishes a methodology to quantify pile setup by using recent field test data that was presented in a companion paper for steel H-piles driven in cohesive soils. Existing methods found in literature for the same purpose either require restrikes of piles onsite or are developed for a specific soil type and seldom use easily quantifiable soil properties, despite their significant influence on pile setup. Following a critical evaluation of the existing methods, a new approach for estimating pile setup was developed using dynamic measurements and analyses in combination with measured soil properties, such as the horizontal coefficient of consolidation, undrained shear strength, and the standard penetration test value. Using pile setup information available in the literature, the proposed approach has shown that it provides good estimates for the setup of steel H-piles, as well as for other types and sizes of driven piles. [ABSTRACT FROM AUTHOR]

In order to study the influence of pile replacement ratio on the performance of composite foundation with rigid-flexible piles, lots of static load tests were carried out in Wenzhou. Pressure cells beneath bearing plate were monitored in the static load test. On basis of test results, the composite foundation settlement with different replacement ratios was investigated, and the influences of different replacement ratio on stress, pile-soil stress ratio and pile-soil load sharing ratio were analyzed. Test results indicate that the rigid pile replacement ratio influences settlement characteristics largely, and the settlement is reduced obviously with the increment of rigid pile replacement. Rigid pile plays an important role in the load bearing in composite foundation. The deformation module is reduced with reduction of rigid pile replacement ratio. When the pile replacement ratio is higher, the rigid pile bearing capacity display is smaller, the flexible pile bearing capacity display is bigger, and the soil bearing capacity display is smaller. [ABSTRACT FROM AUTHOR]

Abstract: Twelve methods to determine axial pile capacity directly based on cone penetration test (CPT) and piezocone penetration test (CPTU) data are presented, compared and evaluated. Analyses and evaluation were conducted on three types of piles of different size and length. All the tested piles have failed at the end of static load test. Both the CPT methods and the CPTU methods were used to estimate the load bearing capacities of the investigated piles (Q p). The static load test was performed to determine the measured load bearing capacities (Q m). The pile capacities determined through different methods were compared with the measured values obtained from the static load tests. Two criteria were selected as bases of evaluation: the best fit line for Q p versus Q m and the arithmetic mean and standard deviation for the ratio Q p/Q m. Results of the analyses showed that the best methods for determining pile capacity are the two CPTU methods. Furthermore, the CPTU method is simple, easy to apply, and not influenced by the subjective judgements of operating staff. Therefore, it is quite suitable for the application in pile engineering practice. [Copyright &y& Elsevier]

Huo, S.; Zhu, M.; Dai, G., and Gong, W., 2020. Application of inclined steel-pipe piles in ocean engineering. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 284–287. Coconut Creek (Florida), ISSN 0749-0208. The bearing capacity of the structure foundation in the ocean engineering is required to be very high due to the long-term bearing complex loads such as wind load, wave load, earthquake and current tide. The inclined steel-pipe pile foundation is widely used in the ocean engineering because its bearing capacity is better than that of the straight pile. Compared with the common steel-pipe piles, the construction and testing of inclined steel-pipe piles are more difficult, with few researches at home and abroad. In this paper, an engineering example is introduced, in which the inclined steel-pipe piles are used as the foundation, and the pile driving barge is used to hammer them to complete the foundation construction of the footbridge. In addition, in order to determine their bearing capacity, the O-cell method is used to carry out field tests on two inclined steel-pipe piles for the first time in China. Finally, the test shows that the bearing capacity of one of the inclined steel-pipe piles is not enough. Then, the pile driving barge is used to hammer it. After the second O-cell test, it is found that the bearing capacity meets the design requirements. [ABSTRACT FROM AUTHOR]

The effects of pile group interaction on settlements were investigated based on the results of two monitoring cases of piled raft foundations and single pile load tests in soft ground. The first case was a piled raft consisting piles embedded in deep dense sand with large spacing supporting a 12-story building, and the case second was a piled raft consisting of friction piles with large spacing supporting a 7-story building. The load-settlement data of the monitored and test piles of different dimensions were compared using a modification factor derived from an elastic solution for the axial response of a single pile. Based on the investigation, it was found that the modified loadsettlement data of the monitored piles were generally consistent with the static load-settlement curve of a single pile. Therefore, no significant effects of pile group interaction on settlement were found. In such cases as pile groups with large spacing, single pile load test data can be more useful in the settlement prediction of piled rafts and pile groups. In addition, it was found that the pile head stiffness of the equivalent static load-settlement curve derived from the rapid load testing in clay soils using the UPM was considerably large compared to the stiffness of the static load test curve, as pointed out by previous studies. [ABSTRACT FROM AUTHOR]